The present invention relates to apparatus and methods for processing substrates such as semiconductor substrates for use in IC fabrication or panels (e.g., glass, plastic, or the like) for use in flat panel display applications. More particularly, the present invention relates to methods and apparatuses that are capable of processing substrates with a high degree of processing uniformity across the substrate surface.
Over the years, plasma processing systems utilizing inductively coupled plasma sources, electron cyclotron resonance (ECR) sources, capacitive sources, and the like, have been introduced and employed to various degrees to process semiconductor substrates and display panels. During the manufacture of these products, multiple deposition and/or etching steps may be employed. During deposition, materials are deposited onto a substrate surface (such as the surface of a glass panel or a wafer). For example, deposited layers such as various forms of silicon, silicon dioxide, silicon nitride, metals and the like may be formed on the surface of the substrate. During etching, materials are selectively removed from predefined areas on the substrate surface. For example, etched features such as vias, contacts, or trenches may be formed in the layers of the substrate.
Referring to FIG. 1, a conventional plasma processing system 10 is shown. In order to process a substrate, a substrate 12 is placed on a substrate pedestal 14 inside a process chamber 16 and a process gas is fed into the process chamber 16. Also, energy is supplied to the process gas to ignite a plasma 18 inside the process chamber 16. After the plasma is ignited, it is sustained with additional energy, which may be coupled to the plasma in various well-known ways, e.g., capacitively, inductively, through microwave, and the like. The plasma is then employed in the processing task, e.g., to selectively etch or deposit a film on the substrate 12. In most situations, a sheath voltage 20 is formed proximate the substrate surface to accelerate the ions of the plasma towards the substrate 12 where they, possibly in combination with other reactants, activate the processing reaction. The sheath voltage is associated with an electrical potential produced between the substrate pedestal 14 and the plasma 18.
Unfortunately, however, the electrical coupling between the substrate pedestal 14 and the plasma 18 tends to be non-uniform, which as a result causes variations in the process performance across the surface of the substrate 12. In particular, the center of the substrate tends to be processed differently than the edge of the substrate, and therefore the yield between the center and edge differ. Accordingly, the edge of the substrate is not generally used to create IC's, which as a result translates into higher costs for the manufacturer. Furthermore, the demand for larger substrates has made it increasingly important to improve process uniformity at the edge of the substrate.
In view of the foregoing, there are desired improved methods and apparatuses for increasing process uniformity at the surface of the substrate.